A man who had been using his cellphone to take upskirt videos decided to buy a spy pen to get his kicks - but was caught in the act when he used it to film a girl in a store.

Chang Wen Rong was found to have recorded upskirt videos of 26 women using the device and his cellphone over 11 months.

He was jailed for 28 weeks yesterday, after pleading guilty earlier to 10 charges, and had the other 16 taken into consideration.

Investigations revealed that in April 2014 - weeks before he was to graduate from the Singapore Management University - Chang bought the pen camcorder on eBay.

On April 29, he went to the Daiso store at Plaza Singapura and spotted a 22-year-old woman in a white skirt. He took out his pen camcorder, clipped it onto his notebook and walked towards the woman from behind, then positioned the camcorder under her skirt - not realising that someone had caught him in the act. The passer-by told the woman and her friend, and police were called.

Twenty-six upskirt videos were found in his mobile phone, pen camcorder, two laptops and hard disk .

His lawyer Josephus Tan said his client has been diagnosed with voyeuristic disorder and is still under treatment. He said after Chang got his first job, he could not hide his offences from his employer, and his services were terminated. Even his girlfriend of four years dumped him.

District Judge Adam Nakhoda noted that Chang committed the offences over a long period of time and agreed with the prosecution that his use of a recording device was an aggravating factor as it would allow for multiple viewings and circulation of the videos. Although the videos were not shared, they were found in Chang's other devices.

"The fact that the accused progressed from using a mobile phone to capture the images to a pen camcorder which, in my opinion, is easier to disguise, would result in sentences above the norm," he said.

The maximum penalty for insulting modesty is one year's jail and a fine.